1. Filed of the Invention
The present invention relates to a semiconductor device. In particular, the present invention relates to technology of a semiconductor device having a display unit (hereinafter referred to as an image display unit) that displays images (video and character information), especially of a passive matrix display device.
2. Related Art of the Invention
Semiconductor devices and, particularly, electronic devices having an image display unit (also referred to as a semiconductor display unit because it is a display unit of a semiconductor device) have been vigorously developed in recent years, and their applications can be represented by such portable devices as game devices, laptops, cellular phones as well as such diversities as liquid crystal TVs, liquid crystal displays, EL displays and so on. As compared to the traditional CRTs, the semiconductor display units can be realized in reduced weights, reduced thickness and consuming electric power in small amounts.
As the conventional semiconductor display units, there have been known a semiconductor display unit of the passive matrix type having a pixel region on which striped electrodes are formed in a manner to intersect each other on the upper and lower sides with the liquid crystal layer or light-emitting layer sandwiched therebetween, and a semiconductor display unit of the active matrix type having a pixel region on which thin-film transistors (hereinafter referred to as TFTs) are arranged like a matrix.
FIG. 2, FIGS. 4A and 4B show an example of a configuration of the passive matrix liquid crystal display device that is an example of traditional semiconductor display units. A description of the configuration will be made as follows.
FIG. 4A shows a block diagram of a display unit (a liquid crystal display unit) of the passive matrix liquid crystal display device. The passive matrix liquid crystal display device has a pixel portion 100, a signal line driving circuit 101, and a scanning line driving circuit 102. A signal line 103 connected to the signal line driving circuit 101 and a scanning line 104 connected to the scanning line 102 are crossed to form the pixel portion 100.
FIG. 4B is a configuration figure of the passive matrix liquid crystal display device. A scanning line and a signal line are formed on substrates 105 and 106 respectively. The signal line driving circuit 109 and the scanning line driving circuit 108 are formed and mounted on the different substrate from that forms pixels. FIG. 4B shows that a driver IC in which the signal line driving circuit 109 and the scanning line driving circuit 108 are formed on the silicon substrate is mounted on an FPC 110 using TAB method. There is another method that the driver IC is mounted on the substrate 105 or 106.
FIG. 2 shows that an example of a cross-sectional view of a pixel region of the passive matrix liquid crystal display device. The pixel region of the passive matrix liquid crystal display device is comprised of two glass substrates (a pair of glass substrate) 201 and 208 sandwiching a liquid crystal layer 205, and a polarizing plate 209. In addition, a reflective electrode 207 and an oriented film 206 are formed on the glass substrate. A color filter 202, a transparent electrode 203, and an oriented film 204 are formed on the glass substrate 201. The glass substrates 208 and 201 are arranged so that the reflective electrode 207 and the transparent electrode 203 are crossed each other. The polarizing plate 209 is comprised of a combination the following; a circle polarizing plate, a linear polarizing plate, a retardation film, and the like.
FIG. 2 shows an example of a reflective liquid crystal display device though, a transparent electrode is used instead of the reflective electrode 207 in the case of the transparent liquid crystal display device.
The description of a configuration of electronic devices having the semiconductor display unit will be made with reference to FIG. 3. FIG. 3 shows a simplified block diagram of a portion relates to an image display.
In FIG. 3, a semiconductor device 301 receives or forms image data, processes the image data, converts the format, and has a function of displaying the image. Examples of the semiconductor device 301 include game devices, video cameras, car navigation systems, personal computers and so on.
On the semiconductor device 301, a pixel region 319 is formed on a substrate having an insulating surface, a scanning line drive circuit 318, a signal line drive circuit 317, and other logic circuits are formed on the different silicon substrates respectively and are mounted in the form of IC chips. Some of the circuit blocks may often be formed on the same silicon substrate.
The semiconductor device 301 is constituted by an input terminal 311, a first control circuit 312, a second control circuit 313, a CPU 314, a first memory 315, a second memory 316, and the semiconductor display unit 302. The input terminal 311 receives data that serve as the basis of image data depending upon the kind of the electronic devices. For example, the input data are those through an antenna in the case of a broadcast receiver, and the input data are those from a CCD in the case of a video camera. The input data may be those from a DV tape or a memory card. The data input through the input terminal 311 are converted into image signals through the first control circuit 312. The first control circuit 312 processes the image signals, such as decoding the image data that are compressed and encoded according to the MPEG standard and the tape format, and interpolating and resizing the image. The image signals output from the first control circuit 312 and the image signals formed or processed by the CPU 314, are fed to the second control circuit 313, and are converted into a format (e.g., scanning format, etc.) that is adapted to the semiconductor display unit 302. The second control circuit 313 produces image signals and control signals of which the formats have been converted.
The CPU 314 efficiently controls the signal processing in the first control circuit 312, second control circuit 313 and other interface circuits. The CPU 314 further forms and processes the image data. The first memory 315 is used as a memory region for storing image data from the first control circuit 312 and for storing image data from the second control circuit 313, as a work memory region for executing the control operation by using a CPU, and as a work memory region at the time of forming the image data by the CPU. As the first memory 315, there can be used a DRAM or an SRAM. The second memory 316 stores the color data and character data, and is necessary when the image data are to be formed or processed by the CPU 314. The second memory 316 is constituted by a mask ROM or an EPROM.
The semiconductor display unit 302 is constituted by the signal line driving circuit 317, scanning line drive circuit 318 and pixel region 319. The signal line driving circuit 317 receives image signals and control signals from the second control circuit 313 (clock signals, start pulse signals and the like), and the scanning line driving circuit 318 receives control signals (clock signals, start pulse signals and the like) from the second control circuit 313. The pixel region 319 displays the image.
The electronic device having the semiconductor display unit can assume a variety of constitutions in addition to the constitution shown in FIG. 3. The simplest constitution may comprise the semiconductor display unit, input/output terminals and a simple control circuit as exemplified by a liquid crystal display or an EL display. When the CPU bears a too large load in the architecture shown in FIG. 3, an image processor may be newly provided to reduce the burden of the CPU.
In electronic equipment that has the semiconductor display unit described above, it is often that before being mounted, a driving circuit and a logic circuit are formed on a substrate different from a substrate on which pixels are formed.
Reduction in size of electronic equipment is now an important object to achieve, as the spread of portable electronic equipment becomes clear. In a semiconductor device structured like this, a lot of IC chips are necessary for mounting aside from a substrate on which pixels are formed and therefore it is not easy to reduce the device in size. Even if logic circuits in the IC chips can be made small, the IC chips need a large margin to mount and it still is difficult to reduce the size of the entire device. On the other hand, if the mounting margin is reduced to make the device smaller, a high mounting technique is required and problems arise in terms of cost and reliability of the mounted parts.